A conventional magnetic recording media has all the servo information buried in a magnetic data layer. The servo information may be overwritten during a writing process of recording data on the magnetic data layer.
FIG. 1 shows a dedicated servo media 100 having a magnetic data layer 102, and a physically separate magnetic layer as a dedicated servo layer 104 for storing the servo information. However, a writing field from a recording/writing head 106 may affect both the magnetic data layer 102 and the dedicated servo layer 104. In other words, the servo information in the servo layer 104 may be overwritten by the writing field.
Thus, it is desirable that the servo layer 104 has a nucleation field which is high enough to be unaffected by the writing field for writing data on the magnetic data layer 102 (in other words, unlimited writing on the magnetic data layer 102). Therefore, the switching field of the servo layer 104 should be large so that it is harder to write on the servo layer 104 than the magnetic data layer 102.
Further, it is also desirable to place the servo layer 104 below the magnetic data layer 102. The servo layer 104 is arranged further from the recording/writing head 106 than the magnetic data layer 102. The head field decay to the servo layer 104 is larger due to the larger magnetic space from the recording/writing head 106 to the servo layer 104. The head field decay to the servo layer 104 may still be large even if a soft underlayer 108 is arranged below the servo layer 104.
As such, it becomes more difficult to write servo information onto the servo layer 104. A conventional recording/writing head may not be able to write servo information onto the servo layer 104 without using energy assisted writing. Further, energy assisted writing may pose complexities and problems for writing onto the servo layer 104. A special energy assist recording/writing head may not be readily available.